lkml.org 
[lkml]   [2003]   [Jan]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patches in this message
/
SubjectEthernet frame padding bug in several drivers - patch(es) included
From
Date

Hi,

I send this mail once before (about 16 hours ago), but it seems it never
reached the list, so I'm resending it. If you recieve it twice I
appologize.


---[ original mail below ]---

Hi,

First of all, please CC me on replies as I'm not subscribed to the list.

I just read a paper by Ofir Arkin and Josh Anderson from @stake
(http://www.atstake.com/research/advisories/2003/atstake_etherleak_report.pdf),
that documents a bug related to incorrect padding of ethernet frames in
many
Linux (and other OS) device drivers.

Briefly, the problem is that when a frame is less than the minimum
required
size, the frame *should* be padded with 0 bytes, but is instead padded
with
kernel memory. This happens since the drivers don't take care to zero
the
padding of the buffer before transmitting it.
I won't repeat the paper here as it does quite a good job explaining the
issue.

After reading the paper I took a look at the source for my 2.4.20
kernel, and
saw that the problem was indeed present in many drivers. I then desided
that
I might as well fix it as anyone else and started on the task.

So far I've only patched 3 drivers (randomly selected), and I would like
to
get some feedback on the patches before I do the rest of them. I would
like
to make sure the fix is correct before spending time implementing a
flawed
fix in all the affected drivers.
The fix is more or less straight from the paper from @stake, so those
people
should get all the credit. I'm just doing the legwork of actually fixing
up
the driver files (patches are against vanilla 2.4.20).

If I get positive feedback on these 3 small patches, then I'll go ahead
and do
the rest of the drivers tomorrow and submit the new patches.

Here are the patches:

patch for drivers/net/3c507.c

--- 3c507.c.orig 2003-01-10 01:51:13.000000000 +0100
+++ 3c507.c 2003-01-10 02:05:30.000000000 +0100
@@ -494,9 +494,16 @@
struct net_local *lp = (struct net_local *) dev->priv;
int ioaddr = dev->base_addr;
unsigned long flags;
- short length = ETH_ZLEN < skb->len ? skb->len : ETH_ZLEN;
+ short length;
unsigned char *buf = skb->data;

+ if (skb->len < ETH_ZLEN) {
+ length = ETH_ZLEN;
+ memset(buf + skb->len, 0, length - skb->len);
+ } else {
+ length = skb->len;
+ }
+
netif_stop_queue (dev);

spin_lock_irqsave (&lp->lock, flags);

patch for drivers/net/atp.c

--- atp.c.orig 2003-01-10 01:51:13.000000000 +0100
+++ atp.c 2003-01-10 02:03:35.000000000 +0100
@@ -553,7 +553,12 @@
int length;
long flags;

- length = ETH_ZLEN < skb->len ? skb->len : ETH_ZLEN;
+ if (skb->len < ETH_ZLEN) {
+ length = ETH_ZLEN;
+ memset(&skb->data + skb->len, 0, length - skb->len);
+ } else {
+ length = skb->len;
+ }

netif_stop_queue(dev);

patch for drivers/net/eepro.c

--- eepro.c.orig 2003-01-10 01:51:13.000000000 +0100
+++ eepro.c 2003-01-10 02:17:00.000000000 +0100
@@ -1138,9 +1138,16 @@
spin_lock_irqsave(&lp->lock, flags);

{
- short length = ETH_ZLEN < skb->len ? skb->len :
ETH_ZLEN;
+ short length;
unsigned char *buf = skb->data;

+ if (skb->len < ETH_ZLEN) {
+ length = ETH_ZLEN;
+ memset(buf + skb->len, 0, length - skb->len);
+ } else {
+ length = skb->len;
+ }
+
if (hardware_send_packet(dev, buf, length))
/* we won't wake queue here because we're out of
space
*/
lp->stats.tx_dropped++;


Best regards,

Jesper Juhl <jju@dif.dk>


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:32    [W:0.037 / U:11.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site